The present application claims priority under 35 U.S.C. xc2xa7 119 of European Patent Application No. 99 11 1193.1, filed on Jun. 9, 1999, the disclosure of which is expressly incorporated by reference herein in its entirety.
1. Field of the Invention
The invention relates to a rotor that can be located within a tank of the paper stock processing machine. The rotor has at least one rotor blade for creating circulation of the stock suspension contained in the tank, and protection against wear is located on a leading front surface of the rotor blade, as viewed in the rotational direction of the rotor.
Further, the invention relates to an anti-wear element for protecting a rotor blade of a rotor located arranged in a tank of a paper stock processing machine. The rotor blades are adapted to circulate a stock suspension contained in the tank.
The invention also relates to a paper stock processing apparatus having at least one rotor blade for creating circulation of a stock suspension in a tank.
2. Discussion of Background Information
A rotor similar in general to that discussed above is known. Normally, it is used not only for circulating the stock suspension, but also for breaking up paper stock contained in the stock suspension. If it is moved directly alongside a screen, it keeps the screen free of blockages and therefore serves as a screen clearer. In this known rotor, wear protection is applied by welding wear-resistant material to the leading front surface of each rotor blade as seen in the rotational direction of the rotor.
The present invention provides a rotor for a paper stock processing machine as well as an anti-wear element for protecting the rotor blades in which or by the use of which the strength of the rotor blades is substantially increased. Replacement of worn parts without damaging the rotor blades is also possible.
According to the present invention, an anti-wear element, adapted to protect against wear, having a base body with at least one wear-resistant working surface is coupled to the rotor blade.
Moreover, the invention also provides an anti-wear element having a base body with at least one wear-resistant working surface and a back side. The anti-wear element is formed to be coupled, e.g., welded, to a leading front edge, as viewed in the rotational direction of the rotor, of the rotor blade to be protected.
In the invention, the anti-wear element is produced separately from a base body and a wear resistant shield and is then welded onto the rotor blade. In this manner, it is possible to eliminate the currently conventional process of welding thick shields onto the rotor blades which adversely affects the material structure of the rotor blades. The welded bond performed according to the present invention only serves to secure the anti-wear element and, therefore, is substantially more gentle to produce. A further advantage is that the edges of the anti-wear element are already preworked before being installed so that time-consuming additional grinding of the edges on the rotor can be omitted.
As soon as the rotor blades of the rotor no longer circulate the stock suspension sufficiently or the paper stock contained in the stock suspension is no longer being broken up sufficiently, the anti-wear element can be removed by separation along the welding seam and can be replaced with a new anti-wear element. The removal and replacement of the anti-wear element preferably occurs after removal of the rotor from the stock processing machine. The replacement of worn rotors can then take place usingxe2x80x9creplacement rotors.xe2x80x9d
It must be assumed that the stress placed on the wear element by forces acting on it during operation is very high. Such forces, however, can be absorbed with little effort if the front surface of the rotor blade and the back surface of the anti-wear element are matched to one another such that a large carrying surface is made available. Then, a relatively weak welding seam is sufficient for a secure fastening and can, if necessary, also be broken.
It is possible to specifically influence the hydraulic effect of the rotor blade by special construction of the anti-wear element, e.g., to change the flow movements within the stock suspension or to increase or decrease the breaking-up effect of the rotor. In this manner, it is possible to equip the paper stock processing machines for different operating conditions without departing from the basic concept of a rotor. In the practice of paper stock processing, there is namely a multitude of different requirements, e.g., because of raw materials.
The present invention is directed to a rotor for a paper stock processing machine. The rotor includes at least one rotor blade having a leading front surface to be protected, and an anti-wear element comprising a base body and at least one wear-resistant surface. The anti-wear element is coupled to the leading front surface.
In accordance with a feature of the present invention, the anti-wear element can be welded to the leading front surface.
According to another feature of the invention, the rotor can be utilized in combination with a tank of a paper stock processing machine. The rotor can be rotatably mounted within the tank to circulate a stock suspension in the tank. Further, the paper stock processing machine can be a primary pulper having a horizontally oriented screen, and the rotor can be rotatably mounted so that the leading front surface positioned adjacent the screen. Alternatively, the paper stock processing machine can be a secondary pulper having a vertically oriented screen, and the rotor can be rotatably mounted so that the leading front surface positioned adjacent the screen.
In accordance with another feature of the instant invention, the at least one wear-resistant working surface can include a layer of wear-resistant material that is firmly coupled to the base. The at least one wear-resistant material may be fixed onto the base body by hard facing. Moreover, the anti-wear element can be formed separately from the rotor, and the anti-wear element may be welded to the at least one rotor blade.
Further, the at least one rotor blade can include a plurality of rotor blade having leading front surfaces, and at least one partial section of each leading front surface of each rotor blade, radially inwardly from a free end, may be completely covered by the anti-wear element.
Moreover, a portion of the anti-wear element coupled to the at least one rotor blade can protrude past the leading front surface. The portion extends past the leading front surface in a direction adapted to face a screen in a paper stock processing machine.
In accordance with still another feature of the present invention, a face of the anti-wear element can be beveled at an angle a of between approximately 1xc2x0 and 45xc2x0 from parallel to a rotational axis of said rotor. Further, the face of the anti-wear element may be beveled such that a radial distance of a surface of the face from the rotational axis increases in a direction toward the leading front surface.
According to a still further feature of the invention, the leading front surface can have one of a cylindrical and conical ring segment shape.
The present invention is also directed to an anti-wear element for protecting a leading front surface of a rotor blade. The anti-wear element includes a base body with a back side, and at least one wear-resistant working surface. The back side is formed to correspond to a shape of, and to be coupled to, the leading front edge.
According to a feature of the invention, the back side may be welded to the leading front edge.
In accordance with another feature of the present invention, the rotor blade protected by the anti-wear coating can be utilized in combination with a tank of a paper stock processing machine. The rotor blades may be adapted to circulate a stock suspension contained in the tank.
Further, the wear-resistant working surface can include a wear-resistant material, and the wear-resistant material can be a non-rusting, alloyed high-grade steel.
In accordance with a still further feature of the invention, the base body can have one of a cylindrical and conical ring segment shape.
Moreover, the wear-resistant working surface may be welded to the base body and the wear-resistant surface can be arranged to form at least one front edge that extends over an edge of the base body opposite the back side. A curvature radius of the front edge can be a maximum of approximately 2 mm.
The present invention is directed to a paper stock processing apparatus. The apparatus includes a tank, a screen, and a rotor rotatably coupled adjacent the screen. The rotor includes at least one rotor blade having a leading front surface, relative to a rotational direction of the rotor, and an anti-wear element coupled to the leading front edge. The anti-wear element includes a base body and a wear-resistant working surface.
According to a feature of the instant invention, the base body may be welded to the leading front surface, and the wear-resistant working surface may be coupled to the base body.
A portion of the anti-wear element may be arranged to protrude past the leading front surface. The portion that extends past the leading front surface in a direction can be adapted to face the screen.
In accordance with yet another feature of the invention, wherein the tank may be a primary pulper tank. Alternatively, the tank may be a secondary pulper tank.